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H2 Receptor Antagonists

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H2 receptor antagonists, also called as H2-blockers are a class of drugs used to block the action of histamine in the stomach. This helps in decreasing the acid production by the parietal cells in the stomach. These drugs are very useful in treating duodenal ulcers and other gastric problems.

What are H2 Receptor Antagonists?

H2 receptor antagonists are medications that help in decreasing the amount of stomach acid. These medications decrease the production of acid in the stomach, by inhibiting the histamine at the H2 receptor cells. Histamine is the enzyme that triggers secretion of gastric acid by acting on the H2 receptor cells. These receptor cells are present in the parietal cells of the gastric mucosa.

How Does H2 Receptor Antagonists Work?

The parietal cells produce the stomach acid. These cells are present in the stomach lining. There are many pathways that stimulate these cells to produce stomach acid. One such way is the stimulation of histamine. These drugs drugs block the signals sent by histamine that triggers the stomach to produce more acid.

Why Are H2 Receptor Antagonists Used?

H2 receptor antagonists help in treating a number of stomach problems. These include:

  • The symptoms of gastroesophageal reflux disease (GERD)
  • Treatment of peptic and duodenum ulcers
  • For treatment of ulcers in stomach caused due to drugs used for treatment of certain types of arthritis
  • Pancreatic problems
  • Hives
  • Dyspepsia

Side Effects of H2 Receptor Antagonists

These medications have been in use since the 1960s. These medications are considered safe to use, but may have certain side effects in some people. These side effects should be bought to the notice of your doctor, if they occur. The side effects of H2 receptor antagonists include:

  • Nausea
  • Muscle pain or weakness
  • Breast enlargement in men
  • Unusual bleeding or bruising
  • Irregular bleeding
  • Yellowing of skin or eyes

Cimetidine is one such drug that can commonly cause adverse drug reactions. Some of the rare adverse side effects include:

  • Headache
  • Tiredness
  • Dizziness
  • Confusion
  • Constipation
  • Rash

Loss of libido, impotence and gynecomastia are often seen with use of cimetidine.

What are the Different Types of H2 Receptor Antagonists?

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The different types of nonprescription or over-the-counter drugs include:

  • Axid AR
  • Pepcid- AC
  • Tagamet-HB
  • Zantact 75

Some of the drugs that require a doctor’s prescription include:

  • Cimetidine
  • Famotidine
  • Nizatidine
  • Ranitidine

Are Proton Pump Inhibitors (PPIs) and H2 Receptor Antagonists Different?

Yes. PPIs and H2 blockers are a different class of drugs. PPIs are more effect than H2 blockers in treatment of gastric problems. The mode of action of both drugs is slightly different. In case of H2 receptor antagonists, they block histamine receptors in the parietal cells in the stomach. The PPIs block the last step in pathway of acid secretion in the stomach. This is the reason, H2 receptor antagonists have a fast action and PPIs have a late effect. But, the effect of PPIs can last up to 24 hours and H2 receptor antagonists work for only 12 hours.

People with kidney problems, liver problems, pregnant women or breastfeeding mothers should avoid H2 receptor antagonist drugs. Although these drugs have a quick action on the symptoms of GERD and ulcers, one should speak to their doctor before taking any of these medications.

Written by: Saptakee sengupta
Date last updated: March 24, 2015